01 -
Preheat your oven to 335°F (170°C). Line a 9-inch square cake pan with parchment paper, making sure the sides are covered too.
02 -
Melt the butter in 30-second microwave bursts until completely liquid. In a large mixing bowl, whisk together both sugars with the melted butter until well combined.
03 -
Gently mix in the eggs, extra yolk, and vanilla - being careful not to incorporate too much air. Then fold in the oil and cocoa powder until the mixture is smooth and uniform.
04 -
Take a small portion of batter and mix it with the red food coloring until completely smooth. Return this vibrant mixture to the main bowl and combine thoroughly.
05 -
Using a rubber spatula, carefully fold in the flour, cornstarch, and salt just until no dry spots remain. Finally, stir in the vinegar until well incorporated. If using, fold in white chocolate chips.
06 -
Pour the batter into your prepared pan and bake for 20-25 minutes. You'll know they're done when a skewer comes out with just a few moist crumbs. Let cool completely before frosting.
07 -
Beat room temperature butter and cream cheese until smooth. Gradually mix in powdered sugar, then beat on high until light and fluffy. Mix in vanilla until well combined.
08 -
Once brownies are completely cool, spread the cream cheese frosting evenly over the top. Slice into squares and serve.